The present invention relates to thrust reversers for jet engines, and more particularly, to anti-deployment mechanisms for thrust reversers.
Jet aircraft, such as commercial passenger and military aircraft, utilize thrust reversers on the aircraft""s jet engines to reduce the aircraft""s speed after landing. One type of thrust reverser used in modern jet aircraft is the cascade type, described in more detail in U.S. Pat. No. 5,448,884. For ease of reference, the description of the cascade type of thrust reverser is substantially reproduced herein.
Referring first to FIG. 1, there is shown a conventional aircraft nacelle indicated at 18 which includes a jet engine, such as a Pratt and Whitney PW4000, indicated at 20 (shown in hidden lines) supported by a strut 22 on a wing 24 (only a portion of which is shown). The nacelle 18 includes a nose cowl 26, a fan cowl 27, a thrust reverser sleeve 28, a core cowl 30 and nozzle exhaust 32. Although some of these components are made up of two mirror image parts split vertically in a clamshell arrangement, each component will be referred to herein as being one piece.
As shown in more detail in FIGS. 2 and 3, the thrust reverser system includes an inner duct (fan duct cowl) 36 and outer sleeve 28. The sleeve 28 translates in an aft direction indicated by an arrow identified by a number 42 in FIG. 2, and a forward direction indicated by an arrow identified by a number 44. When the thrust reverser is deployed, the translating sleeve 28 moves aft from a xe2x80x9cstowedxe2x80x9d position shown in FIG. 1 to a xe2x80x9cdeployedxe2x80x9d position shown in FIG. 2. In this process, cascade vanes 46 (FIG. 2) mounted to a thrust reverser support structure are uncovered. Vanes 46 are slanted in a forward direction so that during thrust reverser operation, fan air from the engine is redirected forward through the vanes (indicated by arrows 47) to aid in decelerating the airplane.
Air driven aft by the engine fan flows along an annular duct 48 (FIGS. 2 and 3) formed by the fan duct cowl 36 and core duct cowl 30. Movement of the sleeve 28 in the aft direction, causes blocker doors 50 to pivot from their stowed positions (shown in FIG. 3) to their deployed positions (shown in FIG. 2) where the doors are positioned to block rearward movement of the air through duct 48. In this manner all rearward movement of the engine fan air is redirected forward through the cascade vanes 46.
Movement of the sleeve 28 is guided along a pair of parallel tracks mounted to the top and bottom of the fan duct cowl 36 in a fore and aft direction. The sleeve 28 is moved between the stowed and deployed positions by means of a number of hydraulic actuators indicated at 54 (FIG. 3), each having an actuator rod 56 which is connected to the sleeve 28. More specifically, as shown in FIGS. 5 and 6, each actuator 54 is connected to a structural torque box 57 via a gimbal mount 61 thereby allowing the actuator to accommodate lateral variances in sleeve motion. As shown in FIG. 4, the actuator rod 56 is located inside the aerodynamic surface of sleeve 28 and is connected to the sleeve 28 by a ball joint 68. The ball joint 68 is accessible by removing a panel 70 which is bolted to the exterior surface of the sleeve 28.
In operation, when the thrust reverser is commanded by the pilot to the deployed position, each actuator rod 56 (FIG. 5) extends in the aft direction. Conversely, when the thrust reverser is commanded by the pilot to move to the stowed position, each actuator rod 56 retracts in the forward direction. In an exemplary embodiment, the actuator 54 is a thrust reverser actuator currently installed on Boeing 767 airplanes.
As shown in FIG. 7, each actuator 54 includes a double acting piston 72 which is extended in the rightward direction (with reference to FIG. 7) by hydraulic pressure acting against a face 74 of the piston 72. Retraction of the piston 72 and the thrust reverser sleeve therewith is accomplished by relieving hydraulic pressure from the piston face 74, so that hydraulic pressure acting against an opposing face 76 of the piston causes it to move in the leftward direction. The piston 72 is connected to the actuator rod 56 which in turn is connected to the thrust reverser sleeve 28 in the manner described previously.
In the exemplary embodiment, each thrust reverser sleeve is driven by three of the actuators 54 (FIG. 3). It is important that each actuator 54 extend and retract the sleeve at the same rate to avoid causing the sleeve to bind along the tracks 51. To accomplish this, operation of each of the three actuators 54 is synchronized by means of an interconnecting synchronizing shaft 80. The sync shaft 80 (FIGS. 5 and 6) is a tube having a stationary outer sleeve and an internal rotating flexible shaft 81 which synchronizes motion of the three actuators. The outer sleeve of the sync shaft 80 is connected to the actuator 54 by a swivel coupling 82.
Thrust reversers include various redundant anti-deployment mechanisms to prevent in-flight deployment, such as locking actuators, non-locking actuators, synchronization shaft locks (sync lock), and auto-restow systems. Thrust reversers presently used on Boeing aircraft have three levels of anti-deployment mechanisms. For example, thrust reversers used on wide body aircraft illustratively have two locking actuators per nacelle and one sync lock per nacelle. Thrust reversers used on narrow body aircraft illustratively have one locking actuator per nacelle, one sync lock per nacelle, and an auto-restow system per nacelle.
It is an object of this invention to provide a hook latch antideployment system that can be used as one of the levels of anti-deployment mechanisms on thrust reversers.
A hook latch antideployment system for a thrust reverser having at least one thrust reverser sleeve that translates between a deployed and stowed positions and a thrust reverser actuation system that translates the thrust reverser sleeve. The thrust reverser has a stationary element that remains stationary with respect to the thrust reverser sleeve when the thrust reverser sleeve translates. The hook latch anti-deployment system has a hook latch a hook member and a latch member. One of the hook and latch members is coupled to the thrust reverser sleeve for translation therewith and the other of the hook and latch members is affixed to the stationary element of the thrust reverser. The hook member engages the latch member when the thrust reverser sleeve is in its stowed position to prevent deployment of the thrust reverser sleeve. The hook latch system further includes a release mechanism coupled to the thrust reverser actuation system that releases the hook member from the latch member when the thrust reverser actuation system is actuated to deploy the thrust reverser sleeve to its deployed position.
In an embodiment, the hook member coupled to the thrust reverser sleeve for translation therewith. The hook member has a hook cam extending from a forward facing side and a latch cam on a bottom side. The latch cam has a concave aft facing portion and a forward facing ramped portion. An actuator is affixed to the stationary element of the thrust reverser. The actuator has a shaft that it extends aftly when the actuator is actuated and actuator a retraction spring that retracts the actuator shaft when the actuator is deactuated. The shaft of the actuator has a roller at an aft end of the shaft that is hooked by the hook cam when the thrust reverser sleeve is in a stowed position and the hook-latch system is in a locked position. A clevis latch has a clevis latch roller at an aft end that is received in the concave aft facing portion of the latch cam when the thrust reverser sleeve is in the stowed position and the hook-latch system is in a locked position. The actuator is coupled to the thrust reverser actuation system wherein the actuator is actuated upon actuation of the thrust reverser actuation system to translate the thrust reverser sleeve aftly to a deployed position. The extension of the actuator shaft upon actuation of the actuator cams the hook cam to cam the hook member to a release position where the latch cam can roll over the clevis latch roller and the hook cam can release from the roller at the aft end of the actuator shaft as the thrust reverser sleeve translates aft.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.